A study evaluation method for line noise filters using common mode output impedance of electrical equipment

Line noise filters are used to suppress conductive noise of electrical equipment and apparatus. Performance of these filters is evaluated by insertion loss. Such evaluation requires the output impedance for common mode noise from equipment. However, the impedance of the equipment under operation is not examined in general. This paper examines the output impedance of the equipment under operation. First, the impedance values are obtained by measurement. From evaluation results of the filter's (common mode capacitor) insertion loss, it is shown that impedance obtained in this paper is effective for verification of line noise filters. Next, an equivalent circuit of the equipment is studied. It is shown that impedance calculated from this equivalent circuit is also effective.